The level up option forces your character past its current level but does not give you the proper XP required to have that level.
You are still getting XP but your total XP has not caught up to your current level.
To fix this, level yourself down until you see your XP bar filled or partially filled.
Then use the ADD XP option until your level is capped out. After your level is capped out, increase your level using the level up option.
Doing it this way takes longer, but it will avoid the issue you are encountering where the character does not have the TOTAL XP to support the current level.
I have the same issue, both of them (the trainer for 1.1.5184 and the trainer for 1.0.5174.0) Main character die as soon as the battle begin. Only the First GEN of this Trainer works for me(but I deleted it) The Improve version's so terrible. This not Improve version, the is unimprove version(both of them: 1.0.5174.0 and Mega Trainer 1.1.5184, the same, the bad )
[Edited by KingTea, 3/16/2011 2:15:56 AM]
[Edited by KingTea, 3/16/2011 2:18:35 AM]
[Edited by KingTea, 3/16/2011 2:18:54 AM]